and Phenomena of Magnetic Induction. 275 



a continuous line in contact (c), we have an experimental ex- 

 ample of the increase of magnetic energy, produced by the in- 

 ductive influence of the particles upon one another. And if we 

 compare the two influences in the case before us, the relative 

 magnetic energies being proportionate to the tangents of the 

 angles of deviation in the compass-needle, we find that the 

 magnetism induced on the separate particles directly by the 

 magnet, was to that induced by the particles upon one another 

 as 2 to 3 nearly. 



This relation, however, is found to vary in diff^erent ferru- 

 ginous bodies, and in the same kind of iron or steel of different 

 degrees of hardness, the transmitted induction, or the influence 

 of particle upon particle, being constantly smaller as the hai*d- 

 ness of the metal increases. This fact, which was first suggest- 

 ed speculatively, by the consideration of the nature of the phe- 

 nomena, was afterwards verified as to iron and steel of three dif- 

 ferent states of hardness, by repeated experiments, of which the 

 following is an example. 



Experiment 2. — Eaamination and illustration of the propor- 

 tiims of directly induced and communicated magnetism in 

 pieces of soft iron, wire-drawn steel, and hard steel. 



The pieces of the different descriptions of metal consisted of 

 six in number of each kind, all very nearly of the same dimen- 

 sions as the wires made use of in the preceding experiment. 

 The magnet was placed about 12 inches from the compass, and 

 j^gth of an inch from the end of the nearest wire ; the series ex- 

 tending 10 inches, brought the other extremity within 2 inches 

 of the centre of the compass. Each series of wires was then suc- 

 cessively interposed between the magnet and compass, at equal 

 intervals from each, and the deviations, in the two arrange- 

 ments b and c of Fig. 6. observed. As, however, the different 

 series of wires were not accurately of the same length, the dis- 

 tance of the magnet from the compass became subject to a 

 small alteration ; but the effbcts of this on the results is not ma- 

 terial. 



